Electric starting motor



May 23, 1933. J. BOHLH 1,910,588

ELECTRIC STARTING MOTOR Filed June 1, 1932 Patented May 23, 1933 UNITED STATES PATENT OFFICE JAKOB BOHLI, OF SOLOTH'URN, SWITZERLAND, ASSIGNOR TO SCINTILLA .AKTIEN- GESELLSCHAFT, OF SOLOTHURN, SWITZERLAND ELECTRIC STARTING MOTOR Application filed June 1, 1932. Serial No. 614,758.

This invention relates to starting motors. the rotor shaft of which is coupled to the pinion shaft by means of an over-running clutch and a multi-disc friction clutch,

known per se, and the pinion of which is moved into engagement by shifting the pinion shaft which extends through the entire length of the armature shaft in such a way that the main switch of the starting motor is closed after the pinion has been moved into full engagement with the ring of teeth of the flywheel.

Starting motors of known design there exists the disadvantage that in case the teeth of the pinion strike against the teeth of the ring of teeth when moving into engagement, the pinion is rotated with respect to the ring of teeth under the full action of the centrifugal mass of the rotor resulting in a rapid wear of the ring of teeth and of the pinion.

According to the invention this disadvantage is overcome by moving simultaneously the pinion shaft into engagement and switching in a special field coil which causes a rotation of the rotor opposite to the working direction of rotation thereby preventing the centrifugal mass of the rotor having a detrimental efiect in case the teeth of the pinion are striking against the teeth of the ring of teeth as the pinion shaft is dragged round only by the friction of the rotating over-running clutch; after the pinion has been moved into engagement the main field coil is switched in and simultaneously the direction of the current in the special field coil changed so that the effect of the magnetic field created by the same is added to the one of the main field coil.

In the accompanying drawing a constructional example of the invention is shown. The preferred form of the device is the only v.nbodiment of the invention illustrated and will now be described in detail, but without implication of limitation beyond the scope of the invention as set forth in the claim.

1 is the rotor of the starting motor comprising the main field coil 2 and the special field coil 3. 7 represents an over-running clutch on which is mounted a multi-disc friction clutch 8, known per se. 5 is the pinion and 4: the pinion shaft capable of being axially displaceable by means of a device as shown for ii stance by 9, thereby moving the pinion into engagement; the pinion is moved out of engagement by the spring 14. 6 re resents the ring of teeth on the flywheel of the internal combustion engine. 1.0 is the contact for switchin in the special field coil 3, 11 the one for th. main field coil 2, whilst the special, field coil is connected parallel to the rotor by the contact 12. 13 represents the battery supplying the whole starting system with current.

in operating the shifting device 9 the special field coil 3 is first switched in by the contact 10. This field coil is so arranged that the electromotor starts to rotate in a direction opposite to working direction of rotation so that the rollers of the over-runnin clutch do not become operative as clutching elements; the pinion shaft is thereby dragged round by the friction of the rotating over-running clutch; in case the teeth of the pinion are striking against the teeth of the ring of teeth; this occurs with a slight shock correspon ding to the friction moment of the overrunning clutch turning in non-operative direction of rotation, increased by the effect of inertia mass of pinion and pinion shaft; as the heavy rotor over-runs the pinion shaft its inertia mass has no effect on the teeth of the pinion and the teeth of the ring of teeth when the latter strike one another. In such a case the driver causes that the pinion shaft and the pinion are moved under the action of the spring 1% by means of the device 9 out of engagement with the ring of teeth; the pinion is then dragged round by the rotor and a slight rotary motion is imparted to the same. This sequence of operations as explained above is repeated by the driver until the pinion can engage in the ring of teeth. After the pinion has fully moved into engagement with the ring of teeth, the main field coil 2 is switched in by further moving the shifting device 9 and simultaneously the special field coil 3 is connected parallel to the rotor.

By the described arrangement of this new starting motor, the wear of the pinion and 10 the ring of teeth of the flywheel is reduced to a minimum.

What I claim is:

In an electric starting motor the combination of a rotor shaft and a inion shaft, the latter coupled to the rotor s aft by means of an over-running clutch and a multi-disc friction clutch, the pinion shaft extending through the entire length of the rotor shaft, and being shifted into engagement by operating a spring loaded lever, a main field coil and a special field coil and switch contacts arranged in such a way that simultaneously the plnion shaft is moved into en ement and said special field coil is switche in causing a rotation of the rotor opposite to the working direction of rotation and that simultaneously after complete engagement of the inion in the ring of teeth the main field is switched in and the direction of the current in the special field coil changed so that the efieot of the magnetic field created by the same is added to the one of the main field coil. In testimony whereof I have signed my name to this specification.

JAKOB BOHLI. 

